I think they're often very well tested, but the documentation piece has always been lacking compared to Elixir.

I used to frequently find myself reading the source code of popular libraries or prying into them at runtime. There's also no central place or format for documentation in ruby. Yes rubydoc.info exists, but it's sort of an afterthought. Sidekiq uses a github wiki, Nokogiri has a dedicated site, Rails has a dedicated site, Ruby itself has yet another site. Some use RDoc, some don't. Or look at Devise https://rubydoc.info/github/heartcombo/devise/main/frames, there's simply nothing documented for most of the classes, and good luck finding in the docs where `before_action :authenticate_user!` comes from.